Hello jessicapinzon. Thanks for visiting healthcaremagic.com. There are many reasons for amenorrhea
1. Pregnancy--if there is a chance that you might be pregnant, you need a pregnancy test. I would advise going to a physician for a blood pregnancy test, anytime, in the US, that you go in for something related to pregnancy or birth control, your parents can not be informed. This is when you are considered an emancipated minor and a doctor does not need parental consent.
2. Reduced body fat due to extreme altheticism
3. PCOS--poly cystic ovarian syndrome--the woman does not ovulate so there is no period.
4. other causes
I would advise that first pregnancy is ruled out as it is the number one cause, if that is done, then investigation can continue.
Be well, Dr. Kimberly